Conventional slit lamp microscopes (U.S. Pat. No. D410,661; Jun. 8, 1999; Wolf, Theodor) are placed on a movable tabletop and positioned between the patient and examiner. The parts of the slit lamp include a joystick base controlled by the examiner, movable arms supporting the light source and optical components, and a chin rest and forehead rest for the patient to place his or her chin and forehead against while leaning forward to be examined. The height of a conventional slit lamp typically positions the base at the stomach region of the average patient and the focal point of the optical components at the eyes. This is problematic when the patient body's shape and size falls outside of the average parameters or when the patient has limited body mobility, which can prevent the patient from being able to reach the chin and forehead rest while in a normal seated position.
More recently, slit lamp manufacturers and inventors have released or proposed modifications to the conventional slit lamp design in attempts to overcome the aforementioned problems, e.g. the handheld slit lamp (U.S. Pat. No. 5,767,942; Jun. 16, 1998; Doherty, Victor J.), portable slit lamp (U.S. Pat. No. 7,083,281; Aug. 1, 2006; Yogesan, Kanagasingam), suspended slit lamp (U.S. Pat. No. 7,736,002; Jun. 15, 2010; Small, Kent W.) and table-free slit lamp (U.S. Pat. No. 7,819,528; Oct. 26, 2010; Dudee, Jitander Singh). However, these prior modifications sacrifice important functions, features and usability of the conventional slit lamp. For example, the handheld and portable slit lamps currently available on the market only have one or two levels of magnification and generally require manual replacement of the ocular lenses to change between magnifications (versus up to five levels of magnification in a conventional slit lamp changeable via rotating drum), fewer filters than a conventional slit lamp, and inability to support many of the peripheral accessories available to conventional slit lamps for enhanced examination procedures (including, but not limited to, background illumination, wratten filtration, applanation tonometry, and specular microscopy); the suspended and table-free slit lamps have not yet been manufactured for the mass market, and as such are untested, but by the nature of their design are more challenging for the examiner to maneuver and operate than conventional slit lamps.
Typically, conventional slit lamp microscopes and associated chin rests used to examine a patient's eyes, are difficult to use for examining large or obese patients (for example over 300 pounds, or 200 pounds for a short person), due to the size and shape of the patient. Although a large or obese patient's head and body can be pushed forward and forced by a doctor's assistant into the chin rest and against the equipment, this can be uncomfortable or painful for the patient.